In a stub switch, known per se to the art, lengths of switch rail are movably mounted between the approach or lead side of the switch and the run out or trailing side of the switch, such that the switch rails form a continuation of the fixed rails and connect the main fixed rails on the approach side to either the main fixed rails on the trailing side or the turnout fixed rails on the trailing side, as selected.
There are a number of ways in which movement of the switch rails between the trailing main rail and trailing turnout rail positions may be effected, and attention is drawn to Canadian Pat. Nos. 87,972, 125,022 and 303,138 which illustrate the use of gauge rods and a plurality of interconnected cam actuators arranged in series along the length of the switch rail, each having a progressively increasing throw so that a relatively long length of switch rail fixed at the approach end thereof may be bent in a controlled curve so that the trailing end thereof can be moved from the main rail position to the turnout rail position.
In the early 1900's, as railway speeds and axis loads increased, stub switches generally fell into disregard and disuse and were largely replaced with split switches which could more readily accept the heavier stresses and strains imparted by the heavier cars. Further, it was very difficult to maintain the old stub switches in alignment with the result that wheels with sharp flanges tended to climb the rails and furthermore such wheels imparted heavy battering loads on the rail ends. As the rails expanded during hot weather the clearance between the rail ends decreased and could even cause a binding condition. In cold weather the rails contracted and the clearance increased substantially, thus compounding the batter problem. In view of these problems the stub switch was superceded by the split switch, but long experience has shown that it too suffers from serious disadvantages. Heavy snow tends to clog split switches and this has to be cleaned out before they can be operated. In desert conditions, blowing sand similarly clogs split switches and has to be removed before operation. Failure to do so can result in twisting or buckling of the switch or its actuating mechanism or in a failure of the switch to open or close properly. The cost of split switches is very high, moreover, as many of the parts require special manufacturing equipment not readily found in machine shops and, furthermore, the life of a split switch is relatively short as the amount of material available in the tapered rails is quite small and is subject to considerable wear and distortion. Thus, it will be appreciated that stub switches have the advantage that they have a longer effective life than split switches, are generally cheaper to manufacture and are not subject to clogging with snow, ice or sand. There is, therefore, a need for an improved stub switch which will avoid the disadvantages of the old stub switches but also avoid the disadvantages of the presently used split switches.